EP3499117A1

EP3499117A1 - Method of determining the pose of a moving head light fixture

Info

Publication number: EP3499117A1
Application number: EP18210755.7A
Authority: EP
Inventors: Niels Jørgen Rasmussen; Christian Quist NIELSEN
Original assignee: Harman Professional Denmark ApS
Current assignee: Harman Professional Denmark ApS
Priority date: 2017-12-15
Filing date: 2018-12-06
Publication date: 2019-06-19
Anticipated expiration: 2038-12-06
Also published as: EP3499117B1; US10859247B2; CN109931574B; CN109931574A; US20190186720A1

Abstract

A method of determining pose of a moving head light fixture, comprising a support structure and a rotatable structure rotatable connected to the support structure. The rotatable structure comprises at least one light source generating a light beam and a position indicating the position of the positing indicator. The method comprises the steps of arranging the position indicator at at least three different positions around said axis of rotation by rotating the rotatable structure; and a step of obtaining the position of the position indicator at each of the at least three different positions. The pose of the moving head light fixture can be obtained based on the obtained positions.

Description

Field of the invention

The present invention relates to a method and system for determining the pose of a moving head light fixture, where the pose indicate the position and orientation of the moving head light fixture in a 3D space.

Background of the Invention

It is known to plan and program light shows using various simulation and visualization software before setting up the actual light show. Such software tool can be used to plan the setup of light truss, light fixtures, video products etc. and to preprogram the light show in a 3D environment using information of the products' performance, position and orientation in the 3D environment. After the virtual planning and programming of the light show the light truss, light fixtures, video products etc. need to be setup in real life and it is difficult to arrange the various products at the exact same positions as planned in the software. As a consequence after the real life installation of light equipment a manual adjustment of the light programming is performed in order to account for a mismatch between the actual position of the products and the virtual position of the products. This is very time consuming especially in connection with touring where the stage nearly on daily basis is taking down and setup at different locations.

Description of the Invention

The object of the present invention is to solve the above described limitations related to prior art. This is achieved by a method and system as described by the independent claims. The dependent claims describe possible embodiments of the present invention. The advantages and benefits of the present invention are described in the detailed description of the invention.

Description of the Drawings

Fig. 1 illustrates a structural diagram of a moving head light fixture;
Fig. 2 illustrates a flow diagram of a method of determining the pose of a moving head light fixture;
Fig. 3 illustrates a flow diagram of another method of determining the pose of a moving head light fixture;
Fig. 4 illustrates a vector diagram illustrating the step of determining the pose based on the obtained positions according to the method of Fig. 3;
Fig. 5 illustrates a vector diagram illustrating another step of determining the pose based on the obtained positions according to the method of Fig. 3;
Fig. 6 illustrates a flow diagram of another method of determining the pose of a moving head light fixture;
Fig. 7 illustrates a vector diagram illustrating the step of determining the pose based on the obtained positions according to the method of Fig. 6;
Fig. 8 illustrates a structural diagram of a moving head light fixture comprising two position indicators;
Fig. 9 illustrates a flow diagram of a method of determining the pose of a moving head light fixture comprising two position indicators;
Fig. 10 illustrates a vector diagram illustrating the step of determining the pose based on the obtained positions according to the method of Fig. 9;
Fig. 11 illustrates a structural diagram of a moving head light fixture comprising a position indicator arranged at the head;
Fig. 12 illustrates a flow diagram of a method of determining the pose of a moving head light fixture comprising a position indicator arranged at the head;
Fig. 13 illustrates a vector diagram illustrating the step of determining the pose based on the obtained positions according to the method of Fig. 12.

Detailed Description of the Invention

The present invention is described in view of exemplary embodiments only intended to illustrate the principles of the present invention. The skilled person will be able to provide several embodiments within the scope of the claims. Throughout the description, the reference numbers of similar elements providing similar effects have been given the same last two digits. Further similar elements providing similar effect within the same figure may be provide with additional characters such as letters or other signs.
Fig. 1 illustrates a structural diagram of a light fixture 101 according to one aspect of the present invention. The light fixture comprises a support structure and a rotatable structure rotatable connected to the support structure. The rotatable structure is rotatable connected to the support structure and is rotatable around an axis of rotation.
In the illustrated embodiment the support structure is provided as a base 103 and the rotatable structure is provided as a yoke 105 where the yoke is rotatable in relation to the base around a yoke axis 107 as indicated by yoke rotation arrow 109. Additionally the yoke comprises a head 111 which is rotatable connected to the yoke and is rotatable in relation to the yoke around a head axis 113 as indicated by head rotation arrow 115.
The rotatable structure comprises at least one light source (not shown) generating a light beam 117 (illustrated in dotted lines). The light source is arranged inside the head and the light beam exists the head through an emitting window 119. The light source can be any kind of light source for instance, incandescent lamps, discharge lamps, plasma lamps, LEDs (light emitting diodes), OLEDs (organic LEDs), PLEDs (polymer LEDs) or combinations thereof. The emitting window is shown as an optical lens configured to deflect the light beam, however it is noticed that the light emitting window can be provided as any component allowing the light beam 117 to propagate through the head housing, such as optical lenses, clear areas, or as an opening in the housing. Additional it is noticed that the light source can also be arranged at the outer surface of the rotatable structure/head. At least one actuator (not shown) is adapted to rotate the rotatable structure around the axis of rotation. For instance a yoke actuator may be configured to rotate the yoke around the yoke axis and a head actuator may be configured to rotate the head around the head rotation axis, as known in the art of entertainment lighting.
The moving head light fixture comprises a controller 121 which controls the components (other subsystems) in the moving head light fixture based on a number of control parameters, such as light effect parameters, position parameters and other parameters related to the moving head lighting fixture. The light effect parameters relate to the light effects that the light beam should generate and may for instance relate to color, dimming level, prism effects, gobo effects, iris effects, animation effects etc. It is noticed that eventual components generating these light effects have not been shown. The position parameters can relate to the position of the head in relation to the yoke and/or position of the yoke in relation to the base. The control parameters can for instance be stored in a memory (not shown) of the light moving head light fixture or be received via an input signal 123. The input signal can be provided as separate signals (not shown) comprising different control parameters and may be provide as wired signals or wireless signals. The light fixture can comprise communication means enabling the moving head light fixture to communicate with other devices such as other light fixtures or light controllers. The moving head light fixture can comprise user input means (not shown) enabling a userto interact directly with the moving head instead of a light controller to communicate with the moving head. The user input means can for instance be buttons, joysticks, touch pads, keyboard, mouse etc. The user input means can also be supported by a display enabling the user to interact with the moving head light fixture through a menu system shown on the display using the user input means. The display device and user input means can in one embodiment also be integrated as a touch screen.
The moving head light fixture comprises a first position indicator 125 arranged at the rotatable structure and at a first position along and offset the axis of rotation. The first position indicator indicates the position of the first position indicator in relation to a reference point 127. The position indicator can be any device cable of indicating the position of the position indicator in relation to the reference point. The position indicator may for instance be based on a global navigation satellite system (GNSS) such as GPS, GLONASS, Galileo, BeiDou etc.; a Wi-Fi positioning system (WPS), bluetooth based positioning systems; radio frequency based position systems, sound/ultrasound position systems, light based positioning systems, accelerometer based positioning systems, gyrometer based positioning systems or combinations thereof. The position indicator can for instance indicate the coordinates of it's position in relation to the reference point 127, for instance in a 3D coordinate system formed by x, y, z axis.
In the illustrated embodiment the first position indicator 125 is arranged at an outer surface of the yoke 105 at a position offset the yoke axis 107 and at the head axis 113. The position indicator is arranged offset the yoke axis at the distance of r.
The pose of the moving head light fixture in relation to the reference point can be obtained using the methods describe below. For instance by configuring the controller 121 to determine the pose of the moving head light fixture based on the methods described below. The moving head light fixture can also form part of a control/positioning system configured to determine the poste of the light fixture, where for instance a central controller is configured to control the moving head light fixture in order arrange the position indicator at different positions and obtain the position of position indicator at these positions.
Fig. 2 illustrate a flow diagram of one embodiment of the method of determine the pose of a moving head light fixture, where the moving head light fixture comprises a support structure and a rotatable structure rotatable connected to the support structure, such that the rotatable structure is rotatable around an axis of rotation. The rotatable structure comprises at least one light source generating a light beam.
The method comprises the steps of:

step 230 of providing a first position indicator at the rotatable structure and at a first position offset the axis of rotation;
step 240 of arranging the position indicator at at least three different positions around the optical axis and obtaining the position of the position indicator at each of the at least three different positions, where the position of the position indicator are obtained in step 241 by using the position indicator and where the position indicator is arranged at the at least three different positions in step 242 by rotating the rotatable structure around the axis of rotation;
step 250 of determine the pose of said moving head light fixture based on said obtained positions of said first position indicator.

The method is in the following described as a method for determine the pose of the moving head light fixture 101 illustrated in Fig. 1.
Step 230 of providing a first position indicator at the rotatable structure and at a first position along and offset the axis of rotation can be performed by arranging the position indicator at the rotatable structure at a position where it is arranged a distance from the axis of rotation. The position indicator can be arrange at any position at the rotatable structure which is offset the axis of rotation resulting in the fact that the position indicator will rotate around axis of rotation upon rotation of the rotatable structure. The position indicator can for instance be provide as a integral part of the rotatable structure, provide inside the rotatable structure, provided at the outer surface of the rotatable structure or at any other position of the rotatable structure. At the moving head light fixture 101 illustrated in Fig. 1 the position indicator 125 is provided at the rotatable structure by arranging the position indicator 125 at the yoke 105 at a position offset the yoke axis 107. In Fig. 1 the position indicator is arrange a distance r from the axis of rotation and will rotate around the yoke axis upon rotation of the yoke.
Step 240 of arranging the position indicator at at least three different positions around the axis of rotation and obtaining the position of the position indicator at each of the at least three different positions can be performed by repeating the step 241 and 242 until the position of the position indicator has been obtained at at least three different positions of the position indicator around the axis of rotation.
Step 241 of obtaining the position of the position indicator 125 can be performed by using the position indicator to indicate its' position in relation to the reference point 127 and storing the indicated position in a memory 222. The position of the position indicator can be stored as any data sat capable of indicating the position of the position indicator. For instance as x,y,z coordinates in relation to the reference point. After the position of the position indicator has been obtained and store in the memory a counter n is increased by 1. The counter n thus indicates the number of obtained positions.
In step 243 tested if the counter n is at least three. It is noted that the method can be setup to require obtaining the position of the position indicator at more than three positions. Thus n can be any number equal to or larger than 3. The number of obtained positions can for instance be increased in order to improve the accuracy of the determined pose of the moving head light fixture.
In case that the number of require obtained positions, n, has not been reached (illustrated by a thumb down) the rotatable structure will in step 242 be rotated in order to arrange the position indicator in a position different from the previously positions where the position has been obtained. Step 241 of obtaining and storing the position of the position indicator is thereafter repeated and the position of the new position is obtained and stored in the memory.
When the number of required obtained positions, n, has been reached (illustrated by a thumb up) a corresponding numbers of positions (larger than 3) have been obtained and stored in the memory 222. The obtained positions p₁, p₂, p₃ ...... p_n may for instance be stored as a number of coordinates p₁[x₁, y₁, z₁], p₂[x₂, y₂, z₂], p₃[x₃, y₃, z₃], ...... p_n[x_n, y_n, z_n], where x_n indicates the x coordinate, y_n indicates the y coordinate and z_n indicates the z coordinator of the position.
The pose of the moving head light fixture is then determined in step 250 based on the obtained positions of the position indicator. Various embodiments of step 250 will be described in further detail in the following part of the description. The output of step 250 is an indication of the pose of the moving head light fixture, where the pose indicates the position p_fix of the moving head light fixture in relation to the reference point 127 and the orientation O _fix the moving head light fixture in relation to the reference point. The position p_fix can be any point of the moving head light fixture for instance a point at the support structure, a point at the rotation structure or a virtual point defined in relation to the moving head light fixture. For instance the position of the moving head light fixture can be indicated as x,y z coordinates in relation to the reference point p_fix[x_fix, y_fix, z_fix].
The orientation of the moving head light fixture can for instance be indicated by an orientation vector O _fix defining the direction of orientation of a part of the moving head light fixture for instance the orientation of the support structure and/or the rotatable structure. The orientation can also indicate the direction of the axis of rotation in relation to the reference point. One orientation vector O _fix may in some applications be enough to define the orientation of the moving head light fixture, however in many application it is also necessary to know the angular orientation of the moving head light fixture in relation to the orientation vector. For instance in connection with a moving head light fixture where the rotatable structure is provided as a yoke carrying a head as described in Fig. 1 it may be necessary to define the angular orientation of the moving head light fixtures in relation to the yoke axis. Consequently the step 250 may comprise a determination of an angular orientation vector OA_fix .
This method makes it possible to obtain the pose of a moving head light fixture in a simple, efficient and reliable way. Once the pose of the moving head light fixture has been obtained it can be communicated to the lighting programming software controlling a light show and the light programming can be adjusted based on the pose of the moving head light fixture. Hereby the manual adjustment of the light programming that is often performed in order to account for a mismatch between the actual position of the products and the virtual position of the moving light head fixture in the 3D visualization software can be automatically performed based on the obtained pose of the moving head light fixture. For instance the pose of all moving head light fixtures in a large lighting setup can be determined based on the method and an adjustment of the light programming can then be performed very fast. Additionally in automatic tracking systems where the moving head light fixture are configured to automatically follow a performer determine automatically the pose of the moving head light fixtures makes it possible to calibrate and setup such automatically tracking systems much faster.
Fig. 3 illustrates and embodiment of the method according to the present invention where step 242 of rotating the rotatable structure comprises a step 344 of rotating the rotatable structure in a predetermined direction of rotation. The result is that the obtained positions can be obtained as a number of constructive positions following a circular path around the axis of rotation. In this embodiment step 250 of determining the posed of the moving head light fixture is in addition to the obtained positions of the position indicator also obtained based on the predetermined direction of rotation and the distance r from the axis of rotation to the positioning indicator. Step 250 comprises a step 351 of obtaining the position of the light fixture, a step 352 of obtaining the orientation of the light fixture and a step 353 of obtaining an angular orientation of the light fixture. The position of the light fixture indicates the position of the light fixture in relation to the reference point 127, the orientation of the light fixture indicates the orientation of the axis of rotation and the angular orientation of the light fixture indicates the angular orientation of the light fixture in relation to the axis of rotation.
The method of Fig. 3 is described in an embodiment where the position of the position indicator is obtained at three positions, thus counter n equals 3. As a consequence three obtained positions p₁, p₂ and p₃ are obtained in step 240. The obtained positions p₁, p₂, p₃ and the distance from the optical axis to the position indicator r are thus inputs to the step 250 of obtaining the pose of the moving head light fixture. The principles of the step 250 of the method in Fig. 3 is described with reference to Fig. 4.
Fig. 4 illustrates a perspective vector diagram illustrating the position of the obtained positions p₁, p₂ and p₃ in relation to the reference point 127. The position of the yoke axis 107 and the head axis 113 are illustrated in the vector diagram and the dotted circle 471 illustrates the circular path of the position indicator when the yoke rotates in relation to the base. The direction of rotation is indicated by arrows 473. The position indicator has been arranged at the same height as the head axis 113 and the dotter circle will thus have center at both the head axis and yoke axis. In the illustrated embodiment the position of the moving head light fixture is consider to be arrange at the intersection between the yoke axis and the head axis and the center of the circle 471 is arrange at this intersection.
The positions can be defined by a number of position vectors starting from the reference point (origin): $\vec{P 1} = (\begin{matrix} x_{1} \\ y_{1} \\ z_{1} \end{matrix})$
$\vec{P 2} = (\begin{matrix} x_{2} \\ y_{2} \\ z_{2} \end{matrix})$
$\vec{P 3} = (\begin{matrix} x_{3} \\ y_{3} \\ z_{3} \end{matrix})$
$\vec{Pfιx} = (\begin{matrix} x_{fix} \\ y_{fix} \\ z_{fix} \end{matrix})$
where vector P1 defines the first obtained position, vector P2 defines the second obtained position; vector P3 defines the third obtained position and vector Pfix defines the position of the moving head light fixture.
Further a radius vector can be defined from the position of the moving head light fixture p_fix to each of obtained positions p₁, p₂ and p₃ and these radius vectors can be found as: $\vec{r 1} = \vec{P 1} - \vec{Pfιx} = (\begin{matrix} x_{1} \\ y_{1} \\ z_{1} \end{matrix}) - (\begin{matrix} x_{fix} \\ y_{fix} \\ z_{fix} \end{matrix}) = (\begin{matrix} x_{1} - x_{fix} \\ y_{1} - y_{fix} \\ z_{1} - z_{fix} \end{matrix})$
$\vec{r 2} = \vec{P 2} - \vec{Pfιx} = (\begin{matrix} x_{2} \\ y_{2} \\ z_{2} \end{matrix}) - (\begin{matrix} x_{fix} \\ y_{fix} \\ z_{fix} \end{matrix}) = (\begin{matrix} x_{2} - x_{fix} \\ y_{2} - y_{fix} \\ z_{2} - z_{fix} \end{matrix})$
$r$ $\vec{3} = \vec{P 3} - \vec{Pfιx} = (\begin{matrix} x_{3} \\ y_{3} \\ z_{3} \end{matrix}) - (\begin{matrix} x_{fix} \\ y_{fix} \\ z_{fix} \end{matrix}) = (\begin{matrix} x_{3} - x_{fix} \\ y \\ _{3} - y_{fix} \\ z \\ _{3} - z_{fix} \end{matrix})$
The length of each of the radius vectors equals r and thus the following equations be set up: $r^{2} = {|\vec{r 1}|}^{2} = {(x_{1} - x_{fix})}^{2} + {(y_{1} - y_{fix})}^{2} + {(z_{1} - z_{fix})}^{2}$
$r^{2} = {|\vec{r 2}|}^{2} = {(x_{2} - x_{fix})}^{2} + {(y_{2} - y_{fix})}^{2} + {(z_{2} - z_{fix})}^{2}$
$r^{2} = {|\vec{r 3}|}^{2} = {(x_{3} - x_{fix})}^{2} + {(y_{3} - y_{fix})}^{2} + {(z_{3} - z_{fix})}^{2}$
The coordinates of Pfix can be found by solving these three equations with respect to x_fix, y_fix, and z_fix
As a consequence in step 351 the position p_fix[x_fix, y_fix, z_fix] of the moving head light fixture can be found using Eq 1Eq 8 to Eq 10.
In order to find the pose of the moving head light fixture the orientation of the moving head light fixture is obtained in step 352. The orientation can be found as an orientation vector O _fix defining the orientation of the moving head light fixture.
The orientation vector O _fix can be found as the cross product between the radius vectors r1, r2 and r3. In this example the step 344 of rotating the rotatable structure in a predetermined direction is performed such that the rotatable structure is rotated less than 180 degrees between two of the obtained positions. The order in which the radius vectors need to cross to obtain the orientation vector is thus defined by the direction of rotation, the order of which the obtained positions p₁, p₂ and p₃ has been obtained and the fact the rotatable structure has been rotated less than 180 degrees between two constrictive obtained positions. The angle between two constructive radius vectors is thus less than 180 degrees and they are both arrange in the plane formed by the circle 471 and the cross product between two constructive radius vectors thus result in an orientation vector which is perpendicular to the plane of the circle. The direction of the orientation vector is defined by the order of which the cross product is found and using the right hand rule makes it possible to obtain the direction of the cross product in relation to the plane formed by the circle. In the illustrated embodiment the cross product between radius vectors r1 and r2 will have a direction which points upwards in relation to the plane of the circle and the same applies to the cross product between r2 and r3.
The orientation vector O _fix can thus be found as: ${\vec{O}}_{fix} = \vec{r 1} \times \vec{r 2}$
Alternatively an alternative the orientation vector O' _fix ca be found as: ${\vec{Oʹ}}_{fix} = \vec{r 2} \times \vec{r 3}$
The orientation vectors O _fix and O' _fix are parallel and indicate the same direction of the moving head light fixture. The pose of the moving head light fixture can thus be obtained where the position of the moving head light fixture is indicated by position p_fix[x_fix, y_fix, z_fix] and where the orientation of the moving head fixture is indicated as the orientation vector O _fix and/or O' _fix.
Fig. 5 illustrates a perspective vector diagram illustrating the position of the obtained positions p₁, p₂ and p₃ and serves to illustrate another embodiment of step 352. In this embodiment step 344 of rotating the rotatable structure in a predetermined direction of rotation is performed such that the total angle of rotation is less than 360 degrees when obtaining the obtained positions. It is thus ensured that all of the obtained points have been obtained within one rotation of the rotatable structure around the yoke axis. Fig. 5 illustrates a similar vector diagram as Fig. 4 and similar elements have been given the same reference numbers and will not be described further.
The coordinates of Pfix and thereby the position p_fix[x_fix, y_fix, z_fix] of the moving head light fixture can be found using Eq 8, Eq 9 and Eq 10 as described previously in connection with Fig. 4.
A number of secant vectors can be defined between each of the obtained positions p₁, p₂ and p₃ and these secant vectors can be found as: $\vec{S 12} = \vec{P 2} - \vec{P 1} = (\begin{matrix} x_{2} \\ y_{2} \\ z_{2} \end{matrix}) - (\begin{matrix} x_{1} \\ y_{1} \\ z_{1} \end{matrix}) = (\begin{matrix} x_{2} - x_{1} \\ y_{2} - y_{1} \\ z_{2} - z_{1} \end{matrix})$
$\vec{S 13} = \vec{P 3} - \vec{P 1} = (\begin{matrix} x_{3} \\ y_{3} \\ z_{3} \end{matrix}) - (\begin{matrix} x_{1} \\ y_{1} \\ z_{1} \end{matrix}) = (\begin{matrix} x_{2} - x_{1} \\ y_{2} - y_{1} \\ z_{2} - z_{1} \end{matrix})$
$\vec{S 23} = \vec{P 3} - \vec{P 2} = (\begin{matrix} x_{3} \\ y_{3} \\ z_{3} \end{matrix}) - (\begin{matrix} x_{2} \\ y_{2} \\ z_{2} \end{matrix}) = (\begin{matrix} x_{3} - x_{2} \\ y_{3} - y_{2} \\ z_{3} - z_{2} \end{matrix})$
Secant vector S23 is not illustrated in Fig. 5 for simplicity of the figure.
The angle between two of the secant vectors is less than 180 degrees, as the obtained points has been obtained during a rotation of the rotatable structure which in total is less than 360 degrees. The secant vectors are also arrange in same plane formed by the circle 471 and the cross product between two secant vectors thus result in an orientation vector O _fix which is perpendicular to the plane of the circle. The direction of the orientation vector is defined by the order of which the secant vectors are crossed and using the right hand rule makes it possible to obtain the direction of the cross product in relation to the plane formed by the circle.
In the illustrated embodiment the cross product between secant vectors S12 and S13 will have a direction which points upwards in relation to the plane of the circle.
The orientation vector O _fix can thus be found as: ${\vec{O}}_{fix} = \vec{S 12} \times \vec{S 13}$
It is to be understood that the orientation vector O _fix can be found as the cross product of many different combinations of secant vectors and the direction of the orientation vector can be found using the right hand rule based on the order of which the secant vectors are crossed. For instance the secant vectors starting from one of the obtained points to the other obtained points can be defined and the cross product between any of these secant vectors will be perpendicular to the plane of the circle. The direction of the resulting orientation vector in relation to the plane can be found based on the direction of rotation.
For instance a first secant vector may be defined from a first obtained position to a second obtained position and a second secant vector may be defined from the first obtained position to a third obtained position, and when the first obtained position, the second obtained position are arrange in chronologic order along the circle and when the orientation vector can be obtained as the cross product between the first secant vector and the second vector the direction of the orientation vector in relation to the plane of the circle can be obtained using the right hand rule.
The orientation vector O _fix (eg. as obtained using methods of Fig. 4 or 5) indicates the orientation of the light moving head light fixture this may in some applications be enough to define the orientation of the moving head light fixture, however in many application it is also necessary to know the angular orientation of the moving head light fixture in relation to the orientation vector. For instance in connection with a moving head light fixture where the rotatable structure is provided as a yoke carrying a head as described in Fig. 1 it may be necessary to define the angular orientation the moving head light fixtures in relation to the yoke axis. Consequently the method may comprise a step 353 of obtaining the angular orientation of the light fixture.
The angular orientation of the moving head light fixture in relation to the axis of rotation can for instance by indicate as an angular orientation vector OA_fix and can be obtained by arranging said first position indicator at at least one predetermined position in relation to the axis of rotation. The predetermined position may for instance be a predetermined position of the rotatable structure in relation to the stationary structure. In a moving head light fixture this can be achieved by instructing the actuators rotating the rotatable structure around the axis of rotation to rotate the rotatable structure into a predetermined angular position. The method can thus comprise a step of arranging said first position indicator at at least one predetermined position in relation to the axis of rotation by rotating said rotatable structure to a predetermined angular position. This step can for instance be performed as a part of step 240 by arranging the position indicator at the predetermined position before obtaining the position of the position indicator.
In the method described in connection with Figs. 3, 4 and 5 the first position p₁ may for instance be a predetermined position were the rotatable structure is arranged at a predetermined position in relation to the stationary structure. The radius vector r1 (found by Eq 5) can be used as an angular orientation vector defining the angular orientation of the support structure around the axis of rotation. Thus: $\vec{{OA}_{fιx}} = \vec{r 1}$
It is noticed that some or all of the positions where the positions indicator is arranged can be can predetermined positions, as a consequence the radius vector defined by each of these positions can be used as an angular position vector defining the angular orientation the light fixture in relation to the axis of rotation.
Fig. 6 illustrate a flow diagram of the method according to the present invention. The method comprises the same steps as described in connection with the method illustrated Fig. 2 and the steps have the same reference numbers as in Fig. 2 and will not be described further.
In this embodiment step 240 is initiated with step 645 of arranging the rotatable structure at a predetermined angular position in relation to the support structure. The predetermined angular position can for instance be indicated by an angle A defining the angle of rotation of the rotatable structure in relation to the support structure, when the rotatable structure have been arranged at the predetermined angular position step 241 of obtaining the position the position indicator 125 is performed.
In this embodiment step 241 comprises a step 646 of obtaining a plurality of positions at the same position of the position indicator. This can be done by performing a plurality of position measurements using the position indicator and store the obtained position measurements in a memory. Thereafter the quality of the measured positions can be verified 647 in order to ensure the in step 241 obtained positions lies within a predetermined tolerance. The verification can for instance be performed by determine the spread of the measured positions and discard the measurements if the spread of the measured positions exceed a predetermined tolerance. Alternatively single measurements can be discarded if they fall outside a predetermined distance to the average position obtained as an average of the measured points. In case the measured points cannot be verified the step 646 can be repeated until the measured positions fulfill the required tolerances. This ensures that the obtained points which in step 250 is used to determine the pose of the light fixture fall within predetermined tolerances and that the pose of the moving head the can be determined with the desired accuracy. Alternatively step 242 of rotating the rotatable structure can be performed before repeating step 646, whereby the position indicator is moved to another position. This makes it possible to obtain the pose of the light fixture despite the position indicator at some positions may not be able to provide an accurate indication of its position for instance due to week signals, signal noise, loss of eye of sight which depends on the position technology that the position indicator is using.
The obtained position of the position indicator at the predetermined position is determined in step 648 based on the plurality of measured positions, for instance bye determining the obtained position as the average position of all the measured positions. This improves the quality of the of the positions and averages measurement errors out.
In this embodiment step 242 of rotating the rotatable structure comprises a step 644 of rotating the rotatable structure in a predetermined direction of rotation and at a predetermined angle of rotation. The predetermined angle of rotation can be any angle within the total angular rotation that the rotatable structure can do in relation to the support structure. In this embodiment the predetermined angle of rotation is obtained as 360 degrees divided by the number of obtained positions n. As a result the rotatable structure rotates 360/n degrees between every position where the position shall be obtained. As a consequence the obtained positions will be distributed equally at a circle around the axis of rotation. The angular orientation of the moving head light fixture in relation to the axis of rotation can as a consequence be obtained based on the plurality of obtained positions. The radius vector from each of the obtained positions can be linked to the angular orientation of the moving head light fixture in relation to the axis of rotation due to the fact that the position of each of the positions points can be linked to the predetermined position obtained in step 645. In the illustrated embodiment the position indicator is arrange in an equal number larger than 4 of positions (n>=4) and the corresponding positions has been obtained at each of these positions. Due to the fact that the rotatable structure is rotated 360/n degrees between every position and that the rotatable structure is arranged in an equal number of positions results in the fact that a number of n/2 position pairs can be obtained; where a position pairs comprises two obtained positions arranged at opposite sides of the circle/axis of rotation. The position pairs can be used to determine the pose of the moving head light fixture as described in connection with step 250 below.
In this embodiment step 250 comprises a step 654 of determining and verifying the distance between the two positions of each position pair. Since the positions of each position pair are arranged at opposite sides of the axis of rotation the distance between the positions of each positions pair should ideally be equal to the diameter of the circle which corresponds to 2r, where r is the distance from the axis of rotation to the position indicator. The position pair is verified by testing that the distance between the two points of the position is within a predefined tolerance. In case the distance between two points of a position pair is not within the predetermined tolerance the position pair can either be disregarded or the step 240 can be repeated in order to ensure prober data. Discarding position pairs without repeating step 240 requires that there are sufficient position pairs to perform the remaining steps of step 250.
Step 651 is a step of determining the position of the moving head light fixture and can for instance be determined based on at least three of the obtained position for instance by using Eq 8, Eq 9 and Eq 10.
In another embodiment the position of the moving head light fixture is obtained by obtaining an average position vector defined by the position vectors of the obtained positions, which is equally arranged along the circle around the axis of rotation. $\vec{P_{fιx}} = \frac{1}{n} \sum_{i = 1}^{n} \vec{P_{n}}$
where P_fix is the position vector of the moving head light fixture obtained as the average vector of the position vectors P_n of the obtained positions. The coordinates of the position vector of the moving head light fixture can be used to define the position of the moving head light fixture p_fix[x_fix, y_fix, z_fix].
In another embodiment the position of the moving head light fixture can be determined by determining the midpoints between the positions of a position pair, as the midpoint between two positions at opposite side of the circle will lie at the center of the circle and can be used as the position of the moving head light fixture. Also the midpoints of all position pairs can be calculate and the average point of all the midpoints can be used as the position of the moving head light fixture. The coordinates of the midpoint or average of midpoints can be used to indicate the position of the moving head light fixture p_fix[x_fix, y_fix, z_fix].
In step 653 at least one angular orientation vector OA_fix indicating the angular orientation of the moving head light fixture in relation to the axis of rotating is determine based on the obtained predetermined positions and defines the angular orientation of the support structure in relation to the axis of rotation. For instance an angular orientation vector can be defined as a vector formed between the positions of a position pair, as a radius vector from the position p_fix[x_fix, y_fix, z_fix] of the moving head light fixture obtained in step 251 to one of the predetermined positions.
In step 652 at least one orientation vector O_fix indicating the orientation of the axis of rotation of the moving head light fixture is determine based on the obtained predetermined positions. The orientation may be defined as described previously as the cross product between two radius vectors or as the cross product between two secant vectors as describe previously. The secant vectors may for instance be defined between the two positions of the of a position pair.
Fig. 7 illustrates a similar vector diagram as Fig. 4 and similar elements have been given the same reference numbers and will not be described further. The vector diagram of Fig. 7 serves to illustrate the method of obtaining the pose of a moving head light fixture as illustrated in Fig. 6. In this example the position indicator is arranged in 4 different positions p₁, p₂, p₃, and p₄. The first position p₁ is obtained by arranging the position indicator at a predetermined position (step 645). In this example the predetermined position corresponds to a zero degree rotation of the rotatable structure in relation to the support structure. As described in connection with Fig. 6 position p₁ is obtained (step 241) by measuring a plurality of positions using the position indicator (step 664), verifying the measured positions (step 647) and providing the position (step 648) as an average of the plurality of position measurements. Then the rotatable structure is rotated 360/4=90 degrees (step 644) and position p₂ is obtained in a similar manner as p₁. Position p₂ is thus obtained at a position where the rotatable structure has been rotated 90 degrees in relation to the support structure. Then the rotatable structure is rotated further 90 degrees (step 644) and position p₃ is obtained in a similar manner as p₁. Position p₃ is thus obtained at a position where the rotatable structure has been rotated 180 degrees in relation to the support structure. Finally the rotatable structure is rotated further 90 degrees (step 644) and position p₄ is obtained in a similar manner as p₁. Position p₄ is thus obtained at a position where the rotatable structure has been rotated 270 degrees in relation to the support structure. The obtained position is stored in a memory and used in step 250 of obtaining the pose of the moving head light fixture.
Positions p₁ and p₃ forms a first position pair as they are arranged at opposite sides of the circle 471 and positions p₂ and p₄ forms a second position pair as they are arranged at opposite sides of the circle 471. The position of the moving head light fixture p_fix[x_fix, y_fix, z_fix] is found as the average point of all the midpoints of the first and second position pair.
The first midpoint can be found as: $\vec{M 1} = \frac{1}{2} (\vec{P 1} + \vec{P 3}) = = \frac{1}{2} (\begin{matrix} x_{1} + x_{3} \\ y_{1} + y_{3} \\ z_{1} + z_{3} \end{matrix})$
where M1 is a vector from the reference point 127 to the first midpoint, P1 is a first position vector from the reference point 127 to the first point p₁ and P3 is a third vector from the reference point 127 to the third point p₃.
The second midpoint can be found as: $\vec{M 2} = \frac{1}{2} (\vec{P 2} + \vec{P 4}) = = \frac{1}{2} (\begin{matrix} x_{2} + x_{4} \\ y_{2} + y_{4} \\ z_{2} + z_{4} \end{matrix})$
where M2 is a vector from the reference point 127 to the second midpoint, P2 is a second position vector from the reference point 127 to the second point p₂ and P4 is a fourth position vector from the reference point 127 to the fourth point p₄.
The position of the moving head light fixture can then be found as: $\vec{P_{fιx}} = \frac{1}{2} (\vec{M 1} + \vec{M 2}) = \frac{1}{2} (\frac{1}{2} (\begin{matrix} x_{1} + x_{3} \\ y_{1} + y_{3} \\ z_{1} + z_{3} \end{matrix}) + \frac{1}{2} (\begin{matrix} x_{2} + x_{4} \\ y_{2} + y_{4} \\ z_{2} + z_{4} \end{matrix})) = \frac{1}{4} (\begin{matrix} x_{1} + x_{2} + x_{3} + x_{4} \\ y_{1} + y_{2} + y_{3} + y_{4} \\ z_{1} + z_{2} + z_{3} + z_{4} \end{matrix})$
In this example the angular orientation and the orientation of the moving head light fixture is determined as a set of x', y' z' orientation vectors, where the orientation vectors are perpendicular to each other. The x', y' orientation vectors are angular orientation vectors determined in step 653 and the z' orientation vector corresponds the orientation vector determined in step 652.
The x' orientation vector O_x indicates the angular orientation of the moving head light fixture along an axis where the rotational structure have been arranged at a rotation of 0 degrees in relation to the support structure. The x' orientation vector O_x can be found as the secant vector from the first position point p₁ to the third position point p₃: $\vec{O_{x}} = \vec{P 1} - \vec{P 3} = (\begin{matrix} x_{1} - x_{3} \\ y_{1} - y_{3} \\ z_{1} - z_{3} \end{matrix})$
The y' orientation vector O_y indicates the angular orientation of the moving head light fixture along an axis where the rotational structure have been arranged at a rotation of 90 degrees in relation to the support structure. The y' orientation vector O_y can be found as the secant vector from the second position point p₂ to the fourth position point p₄: $\vec{O_{y}} = \vec{P 2} - \vec{P 4} = (\begin{matrix} x_{2} - x_{4} \\ y_{2} - y_{4} \\ z_{2} - z_{4} \end{matrix})$
The x' and y' orientation vectors is found in step 653 of the method illustrated in Fig. 6.
The z' orientation vector indicates the orientation of the moving head light fixture and is perpendicular to the plane formed by the x' and y' orientation vectors and can thus be found as the cross product between the x' and y' orientation vectors: $\vec{O_{z}} = \vec{O_{x}} \times \vec{O_{y}}$
The order of which the x' and y' orientation vectors are crossed is determined by the direction of rotation. The z' orientation vector will point downwards in relation to the support structure if the rotatable structure is rotated in the counter clockwise direction in relation to the support structure and z' orientation vector will point upwards in relation to the support structure if the rotatable structure is rotated in the clockwise direction in relation to the support structure.
In this example the pose of the moving head light fixture is thus indicated by:

the position of the moving head light fixture at the position where the yoke rotation axis and head rotation axis intersects;
a x' orientation vector indicating the orientation of the head rotation axis when the rotatable structure (the yoke) is rotated zero degrees in relation to the support structure (the base);
a y' orientation vector indicating the orientation of the head rotation axis when the rotatable structure (the yoke) is rotated 90 degrees in relation to the support structure (the base); and
a z' orientation vector indicating the orientation of the yoke rotation axis in a direction away from the support structure.

Fig. 8 illustrates a structural diagram of a light fixture 801 according to one aspect of the present invention. The light fixture 801 are substantially identical to the light fixture illustrated in Fig. 1 and identical features have been given the same reference numbers and will not be described in further detail. In this embodiment the light fixture comprises a second position indicator 826 arranged at the rotatable structure and at a second position along and offset the axis of rotation. The second position indicator indicates the position of the second position indicator in relation to a reference point 127. The second position indicator can be any device cable of indicating the position of the position indicator in relation to the reference point. The position indicator may for instance be based on a global navigation satellite system (GNSS) such as GPS, GLONASS, Galileo, BeiDou etc.; a Wi-Fi positioning system (WPS), bluetooth based positioning systems; radio frequency based position systems, sound/ultrasound position systems, light based positioning systems, accelerometer based positioning systems, gyro meter based positioning systems or combinations thereof. The second position indicator can for instance indicate the coordinates of its position in relation to the reference point 127, for instance in a 3D coordinate system formed by x, y, z axis.
Fig. 9 illustrate a flow diagram of one embodiment of the method of determining the pose of a moving head light fixture, where the moving head light fixture comprises a support structure and a rotatable structure rotatable connected to the support structure, such that the rotatable structure is rotatable around an axis of rotation. The rotatable structure comprises at least one light source generating a light beam. The method is described as a method for determine the pose of the moving head light fixture 801 illustrated in Fig. 8. The method comprises the same steps as the method illustrated in figure 2 and similar method steps have been given the same reference numbers and will not be described in further detail.
In this embodiment step 930 of providing a first position indicator at the rotatable structure and at a first position along and offset the axis of rotation comprises also a step of providing a second position indicator at the rotatable structure and at a second position. This step can be performed by arranging the position indicators at the rotatable structure at a position where they are arranged a distance from the axis of rotation. The position indicators can be arrange at any position at the rotatable structure which is offset the axis of rotation resulting in the fact that the position indicator will rotate around the axis of rotation upon rotation of the rotatable structure. The position indicators can for instance be provide as an integral part of the rotatable structure, provided inside the rotatable structure, provided at the outer surface of the rotatable structure or at any other position of the rotatable structure. The first and second position indicators are further arrange at different positions along the axis of rotation. At the moving head light fixture illustrated in Fig. 8 the first position indicator 125 is provide at the rotatable structure by arranging the position indicator 125 at the yoke 105 at a position offset the yoke axis 107. In Fig. 8 the first position indicator is arrange a distance r from the axis of rotation and will rotate around the yoke axis upon rotation of the yoke. Similar the second position indicator 826 is provide at the rotatable structure by arranging the position indicator 826 at the yoke 105 at a position offset the yoke axis 107. The second position indicator is arrange a distance r' from the axis of rotation and will rotate around the yoke axis upon rotation of the yoke. It is to be understood that the distances r and r' may be the same or different. The first and second position indicators are further arrange at different positions along the axis of rotation and separated by distance d.
Step 240 of arranging the position indicators at at least three different positions around the axis of rotation axis and obtaining the position of the position indicators at each of the at least three different positions can be performed by repeating the step 941 and 242 until the position of the position indicators have been obtained at at least three different positions around the axis of rotation.
Step 941 of obtaining the position the positions indicator 125 and 826 can be performed by using the position indicators to indicate their positions in relation to the reference point 127 and storing the indicated positions in a memory 222. The positions of the position indicators can be stored as any data sat capable of indicating the positions of the position indicators. For instance as x,y,z coordinates in relation to the reference point. Thereafter it is tested 243 if the positions have been obtained at at least three different positions and is not the case then the rotatable stricture in rotated in step 242.
The obtained positions p₁, p₂, p₃...... p_n of the first position indicator may for instance be stored as a number of coordinates p₁[x₁, y₁, z₁], p₂[x₂, y₂, z₂], p₃[x₃, y₃, z₃], ...... p_n[x_n, y_n, z_n], where x_n indicates the x coordinate, y_n indicates the y coordinate and z_n indicates the z coordinator of the position. Similar the obtained positions p'₁, p'₂, p'₃ ...... p'_n of the second position indicator may for instance be stored as a number of coordinates p'₁[x'₁, y'₁, z'₁], p'₂[x'₂, y'₂, z'₂], p'₃[x'₃, y'₃, z'₃], ...... p'_n['x_n, y'_n, z'_n], where x'_n indicates the x coordinate, y'_n indicates the y coordinate and z'_n indicates the z coordinator of the position.
Fig. 10 illustrates a similar vector diagram as Fig. 4 and similar elements have been given the same reference numbers and will not be described further. The vector diagram of Fig. 10 serves to illustrate the method (Fig. 9) of obtaining the pose of a moving head light fixture as illustrated in Fig. 8. The positions obtained in step 240 and the corresponding position vectors are illustrated in the vector diagram. The positions p₁, p₂, p₃....p_n obtained by the first position indicator will be positioned in a first circle 471 and the positions p'₁, p'₂, p'₃....p'_n obtained by the second position indicator will be positioned on a second circle 1072.
In this embodiment step 250 of determine the pose of the moving head light fixture comprise a step 351 of obtaining the position p_fix[x_fix, y_fix, z_fix] of the light fixture based on the obtained positions of the first position indicator and Eq 8 to Eq 10 as described previously.
In this embodiment step 250 of determine the pose of the moving head light fixture comprise a step 955 of obtaining the center p'_fix[x'_fix, y'_fix, z'_fix] of the second circle 1072 formed by the obtained positions of the second position indicator. The second position indicator will like the first position indicator perform a circular rotation 1072 around the yoke axis and the obtained positions of the second position indicator p'₁, p'₂ and p'₃ will thus be positioned on this circle. The center of the circle P'_fix can be found using the obtained positions p'₁, p'₂, p'₃ and the distance from the axis of rotation the second position indicator r' in Eq 8 to Eq 10 as a result the center of the second circle p'_fix[x'_fix, y'_fix, z'_fix] can be found.
In this embodiment and in step 952 the orientation of the moving head light fixture O'_fix is obtained based on the position p_fix[x_fix, y_fix, z_fix] of the moving head light fixture and the center of the second circle p'_fix[x'_fix, y'_fix, z'_fix]: $\vec{{Oʹ}_{fιx}} = \vec{{Pʹ}_{fιx}} - \vec{P_{fιx}} = (\begin{matrix} {xʹ}_{fix} - x_{fix} \\ {yʹ}_{fix} - y_{fix} \\ {zʹ}_{fix} - z_{fix} \end{matrix})$
where P_fix is the position vector of position p_fix and P'_fix is the position vector of position p'_fix.
Using two position indicators makes it possible to obtain the orientation vector without knowing the direction of rotation.
The angular orientation of the moving head light fixture can be determined in step 353 as described previously.
Fig. 11 illustrates a structural diagram of a light fixture 1101 the according to one aspect of the present invention. The light fixture 1101 are substantially identical to the light fixture illustrated in Fig. 1 and identical features have been given the same reference numbers and will not be described in further detail. In this drawing the light fixture 110 is illustrated from the side and the head axis 113 is thus perpendicular to the plane of the drawing. As previously described the head is rotatable around the head axis 113 as indicated by arrow 115 and the head 111 is in dotted lines illustrated in a first position where the head is rotated 90 degrees in relation to the yoke axis and the light beam 117 is in this position substantially parallel with the base. In solid lines the head 111 is illustrated in as second position where the head is rotated 0 degrees in relation to the yoke axis and the light beam 117 is substantially directed upwards in relation to the base.
In this embodiment the light fixture comprises a first position indicator 1125 arranged at the head 111 and the position indicator indicates the position of the first position indicator in relation to a reference point 127 as described previously. The position indicator 1125 will thus move in relation to the yoke axis upon rotation of the head and in the first position of the head be arranged at a distance r from the yoke axis and distance D along the head axis. In the second position of the head the first position indicator 1125 is arrange a distance r' from the yoke axis and distance D' along the head axis.
Fig. 12 illustrate a flow diagram of one embodiment of the method of determine the pose of the moving head light fixture illustrated in Fig. 11. The method comprises substantial identical steps as described in connection with the previous described method steps
In this embodiment step 1230 of providing a first position indicator at the rotatable structure and at a first position along and offset the axis of rotation is performed by arranging the first position indicator at the head of a moving head light fixture where the head is rotatable in relation to a yoke, which is rotatable in relation to a base. The position indicators can be arrange at any position at the head which is offset the yoke axis resulting in the fact that the position indicator will rotate around the yoke axis upon rotation of the yoke. The position indicators can for instance be provide as an integral part of the head, provided inside the head, provided at the outer surface of the head or at any other position of the head.
Step 240 of arranging the position indicators at at least three different positions around the axis of rotation axis and obtaining the position of the position indicators at each of the at least three different positions can be performed by repeating the steps 241 and 242 until the position of the position indicators have been obtained at at least three different positions around the axis of rotation.
In this embodiment the repetition steps 241 and strep 242 is performed with the head at at least two different positions in relation to the yoke axis. In this embodiment this is performed in step 1243 verifying that at at least three positions have been obtained with the head at at least two different position in relation to the yoke axis. This can for instance be done by increasing a counter t by 1 every time test 243 is OK and then in 1243 test if the counter t is at least 2. If test 1243 is negative then a step 1249 of rotating the head in relation to the head axis is performed, whereby the head is arranged at a different position in relation to to the yoke axis. Steps 241 and 242 is then repeated until at least three positions of the position indicators around the yoke axis is obtained. It is noted that the at least three positions of the position indicator around the yoke axis can be performed at more than two positions of the head in relation to the yoke.
The obtained positions p₁, p₂, p₃ ...... p_n of the first position indicator with the head at the first position may be stored as a number of coordinates p₁[x₁, y₁, z₁], p₂[x₂, y₂, z₂], p₃[x₃, y₃, z₃], ...... p_n[x_n, y_n, z_n], where x_n indicates the x coordinate, y_n indicates the y coordinate and z_n indicates the z coordinator of the position. Similar the obtained positions p'₁, p'₂, p'₃...... p'_n of the first position indicator with the head at the second position may for instance be stored as a number of coordinates p'₁[x'₁, y'₁, z'₁], p'₂[x'₂, y'₂, z'₂], p'₃[x'₃, y'₃, z'₃], ...... p'_n['x_n, y'_n, z'_n], where x'_n indicates the x coordinate, y'_n indicates the y coordinate and z'_n indicates the z coordinator of the position.
Fig. 13 illustrates a similar vector diagram as Fig. 10 and similar elements have been given the same reference numbers and will not be described further. The vector diagram of Fig. 12 serves to illustrate the method (Fig. 12) of obtaining the pose of a moving head light fixture (Fig. 11). The positions obtained in step 240 and the corresponding position vectors are illustrated in the vector diagram. The positions p₁, p₂, p₃....p_n obtained by the first position with the head at the first position will be positioned in a first circle 1371 and the positions p'₁, p'₂, p'₃....p'_n obtained by the second position indicator will be positioned on a second circle 1372.
In this embodiment step 250 of determining the pose of the moving head light fixture comprise a step 1256 of obtaining the center p_c1[x_c1, y_c1, z_c1] of the first circle 1371 formed by the obtained positions of the position indicator with the head at the first position. The center of the circle P_c1 can be found using the obtained positions p₁, p₂, p₃....p_n and the distance from the axis of rotation the second position indicator r using Eq 8 to Eq 10 as a result the center of the second circle p_c1[x_c1, y_c1, z_c1] can be found. Alternatively Eq 18 can also be used to find the center of the first circle.
In this embodiment step 250 of determining the pose of the moving head light fixture comprise a step 1255 of obtaining the center p_c2[x_c2, y_c2, z_c2] of the second circle 1372 formed by the obtained positions of the position indicator with the head at the second position. The center of the circle P_c2 can be found using the obtained positions p'₁, p'₂, p'₃....p'_n and the distance from the axis of rotation the second position indicator using Eq 8 to Eq 10 as a result the center of the second circle p_c2[x_c2, y_c2, z_c2] can be found. Alternatively Eq 18 can also be used to find the center of the second circle.
In this embodiments and in step 1252 the orientation of the moving head light fixture O _fix is obtained based on the center of the first and second circles using: $\vec{O_{fιx}} = \vec{P_{c 1}} - \vec{P_{c 2}} = (\begin{matrix} x_{c 1} - x_{c 2} \\ y_{c 1} - y_{c 2} \\ z_{c 1} - z_{c 2} \end{matrix})$
where P _c1 is the position vector of position p_c1 and P _c2 is the position vector of position p_c2.
In this embodiments and in step 1251 the position of the moving head light fixture, p_fix[x_fix, y_fix, z_fix] is obtained based on the center of the first and second circles and the orientation vector obtained in step 1252. In this embodiment the position of the moving head light fixture is defined at the interception of the yoke axis 107 and the head axis 113. The position vector P_fix can be found as: $\vec{P_{fιx}} = \vec{P_{c 2}} + Dʹ \frac{1}{|\vec{O_{fιx}}|} \vec{O_{fιx}}$
where P _c2 is the position vector of position p_c2, D' the distance along the yoke axis from the head axis to the position indicator when the head is arranged in the second position and $\frac{1}{|\vec{o_{fix}}|} \vec{o_{fix}}$
is the unit-vector of the orientation vector.
Alternatively the position vector P_fix can be found as: $\vec{P_{fιx}} = \vec{P_{c 1}} - D \frac{1}{|\vec{O_{fιx}}|} \vec{O_{fιx}}$
where P _c1 is the position vector of position p_c12, D the distance along the yoke axis from the head axis to the position indicator when the head is arranged in the first position and $\frac{1}{|\vec{o_{fix}}|} \vec{o_{fix}}$
is the unit-vector of the orientation vector.
The angular orientation of the moving head light fixture can be determined in step 453 as described previously where one of the obtained positions is to be considered as a predetermined position.
It is to be understood that the methods of determining the pose of a moving head light fixture described previously can be combined and that some method steps of one of the described methods may be used in other of the described methods.
The method can be embodied into various systems for instance the methods may be implemented directly into the processor of a moving head light fixture in such system the position indicators shall be able to determine their position internally and provide the positions to the processor of the moving head light fixture. In such system the moving head light fixture can be configured to send the pose of the moving head light fixture directly to a central controller such as a light controller, light controller software or a visualization software.
It is also possible to embody the method into a system where a central controller sends control commands to the moving head light fixture and thereby ensure the moving head light fixtures performs the rotations/movements as described in the methods. The positions of the position indicator can then be determined by a position determine system which determines the positions of the positions indicator at the various positions and sends these position to the central controller. The central controller is then configured to determining the pose of the moving head light fixture based on the received data. Thus the various calculations can be done in the light fixture, in a central controller or in positioning system.
It is noticed the position indicator can be based on ultrasound technology, Radio frequency based or light based technology. The position indicator may for instance be provided as a transmitter sending out a reference signal in sound, ultrasound, radio frequency or light. A number of receivers can then be provided at the surroundings of the position indicator and these receivers receives the reference signal from the transmitter and a controller can be configured to determine the position of the position indicator based on the signals received by the receivers. For instance based on the time delay that the different receivers receive the reference signals, based on the level of the reference signal etc.

In one embodiment the positioning system is based on ultrasound, the position indicator sends ultrasound which then is received by a number of receivers which based on delay of the ultra sound determines the position of the moving head light fixture. Opposite system where a number of transmitters is arrange around the light fixture and which sends ultrasound where position indicator determines it position based on delay between different ultrasound send by the transmitters is also possible. For instance as disclosed in WO 95/14241 , us6141293 , us6316934 , us 6484131 , us 6487516 , wo06102844 , WO08005931 or WO11054358 . Similar system can be set up using RF transmitters and receivers.

List of references

101, 801, 1101	light fixture
103	base
105	yoke
107	yoke axis
109	yoke rotation arrow
111	head
113	head axis
115	head rotation arrow
117	light beam
119	emitting window
121	controller
222	memory
123	input signal
125, 1125	first position indicator
826	second position indicator
27	reference point
230	providing position indicator at rotatable structure
930	providing first and second position indicators at rotatable structure
1230	providing position indicator at head
240	Arrange position indicator and obtain positions
241, 941	obtain position
242	Rotate rotatable structure
243	Test number of obtained positions is at least 3
443	Test number of obtained positions is at least 4
1243	Test number of head positions is at least 2
344	rotate in predetermined direction
644	rotate 360/n degrees in predetermined direction
645	Arrange position indicator at predetermined position
646	obtain a plurality of position measurements
647	verify measured position elements
648	provide position element
1249	rotate head
250	Determine pose of light fixture based on obtained positions
351, 651, 1251	obtaining position of light fixture
352, 652, 952, 1252	Obtaining orientation vector of light fixture
353, 653, 453	Obtaining angular orientation
654	verify distance between positions of position pair
955, 1255	obtain center of 2nd circle
1256	obtain center of 1st circle
471	Circular path of first position indicator
1072, 1372	2nd circular path
473	Direction of rotation of rotatable structure

Claims

A method of determining the pose of a moving head light fixture, wherein said moving head light fixture comprises a support structure and a rotatable structure, said rotatable structure is rotatable connected to said support structure and is rotatable around an axis of rotation and said rotatable structure comprises at least one light source generating a light beam, said rotatable structure comprises a first position indicator at said rotatable structure, said position indicator is arranged at a first position offset said axis of rotation, said first position indicator indicates the position of said first position indicator in relation to a reference point;
said method comprising the steps of:
- arranging said first position indicator at at least three different positions around said axis of rotation and obtaining the position of said position indicator at each of said at least three different positions, where said position of said position indicator are obtained by using said position indicator and where said position indicator is arranged at said at least three different positions by rotating said rotatable structure around said axis of rotation;

- determining the pose of said moving head light fixture based on said obtained positions of said first position indicator.
The method according to claim 1, characterized in that said step of determining the pose of said moving head light fixture comprises a step of determining an orientation vector, where said orientation vector indicates the orientation of said rotation axis in relation to a reference point and a step of determining the position of said moving head light fixture in relation to said reference point.
The method according to any one of claims 1-2, characterized in that said step of determining the pose of said moving head light fixture comprises a step of determining an angular orientation vector, where said angular orientation vector indicates the angular orientation of said moving head light fixture in relation to said axis of rotation.
The method according to any one of claims 1-3, characterized in that said step of obtaining the position of said first position indicator at said at least three different positions comprises a step of rotating said rotatable structure in a predetermined direction of rotation and in that said step of determining the pose of said moving head light fixture is further based on said direction of rotation.
The method according to any one of claims 1-4, characterized in that said step of arranging said first position indicator at at least three different positions around said axis of rotation comprises a step of arranging said first position indicator at at least one predetermined position; and in that said step of determining the pose of said moving head light fixture is further based on said at least one predetermined position.
The method according to claims 3 and 5, characterized in that said step of determining said angular orientation vector is based on said at least one predetermined position.
The method according to any one of claims 1-6, characterized in that said step of determining the pose of said moving head light fixture is based on a predetermined distance, where said predetermined distance indicates the distance from said axis of rotation to said first position indicator
The method according to any one of claims 1-7, characterized in that said method comprises the steps of:
- arranging said first position indicator at another position along said axis of rotation, where said another position is different from said first position along said axis of rotation,
and at said another position:
- arranging said first position indicator at at least three positions around said axis of rotation by rotating said rotatable structure around said axis of rotation; and

- obtaining the position of said first position indicator at each of said at least three different positions using said position indicator;
and in that said step of determining the pose of said moving head light fixture is further based on said obtained positions of said first position indicator at said another position.
The method according to any one of claims 1-7, characterized in that said moving head light fixture comprises a second position indicator at a second position offset said axis of rotation and at a second position along said axis of rotation, said second position along said axis of rotation is different from said first position along said axis of rotation, said second position indicator indicates the position of said second position indicator in relation to said reference point;
said method comprising the steps of:
- arranging said second position indicator at at least three positions around said axis of rotation by rotating said rotatable structure around said axis of rotation;

- obtaining the position of said second position indicator at each of said at least three different positions using said second position indicator;
when said step of determining the pose of said moving head light fixture is further based on said obtained positions of said second position indicator.
The method according to any one of claims 1-9, characterized in that any one of said steps of obtaining the position of any one of said position indicators comprises a step of obtaining a plurality of position measurements at each of said different positions and said obtained positions of any one of said position indicators are obtained based on said plurality of position measurements.
The method according to claim 10, characterized in that any one of said steps of obtaining the position of any one of said position indicators comprises a step of obtaining the statistically spread of said plurality of position measurements and discarding position measurements falling out of outside a predetermined spread tolerance.
The method according to any one of claims 1-11, characterized in that any one of said steps of arranging any one of said position indicators at at least three positions around said axis comprises a step of arranging said position indicator at two positions opposite each other in relation to said axis of rotation by rotating said rotatable structure 180 degrees in relation to said axis of rotation.
The method according to any one of claims 1-12, characterized in that said method comprises a step of providing said first position indicator at said first position of said rotatable structure.
The method according to any one of claims 9-12, characterized in that said method comprises a step of providing said second position indicator at said second of said rotatable structure.
A system for determining the pose of a moving head light fixture, where said system comprises:
• at least one moving head light fixture comprising a support structure and a rotatable structure, said rotatable structure is rotatable connected to said support structure and is rotatable around an axis of rotation and said rotatable structure comprises at least one light source generating a light beam, said rotatable structure comprises a first position indicator indicating the position of said first position indicator in relation to a reference point and said first position indicator is arranged offset said axis of rotation; and

• a controller configured to arrange said first position indicator at at least three different positions around said axis of rotation and to obtain the position of said position indicator at each of said at least three different positions, where said position of said position indicator are obtained from said position indicator and wherein said position indicator is arranged at said at least three different positions by rotating said rotatable structure around said axis of rotation; wherein said controller is further configured to determine the pose of said moving head light fixture based on said obtained positions of said first position indicator.
The system according to claim 15, characterized in that said controller is configured to determine to pose of said moving head light fixture based on the method according to any one of claims 1-13.
The system according to any one of claims 15-16, characterized in that said controller is provided as a central light controller connected to said moving head light fixture, said central light controller is configured to send control signals to said moving head light fixture and said controller is configured to rotate said rotatable structure of said moving head light fixture by sending control signal indicative of said rotation to said moving head light fixture and said central light controller is configured to receive said position of said position indicator from a position system comprising said position indicator.